Hydraulic tractor drive



l1g- 14, 1951 J. s. RoBBlNs HYDRAULIC TRACTOR DRIVE 3 Sheets-Sheet 1 Filed June 21 1950 llh/ Aug. 14, 1951 J. s. ROBBINS 2,564,608

HYDRAULIC TRACTOR DRIVE Filed June 21, 1950 3 Sheets-Sheet 2 FIG. 4 FIG. 5

VIII/1,

IN V EN TOR.'

JAMES S. RCBBINS ug- 14, 1951 J. s. RolssBlNsv HYDRAULIC TRACTOR DRIVE 3 Sheets-Sheet 5 Filed June 2l 1950 Patented Aug. 14, 1951 AUNI TED EN T v.UFF ICE :2,564,608 kfmzmmULIo TRA-cron DRIVE Jamesancbbms, rngmanarai-k; nl.

fApplication June21, 1950;;5Serial No. 169,408

111`Claims.

`l .The main objectsof .this invention areto provide an'improvedzfor-m of operating mechanism -for-..endless chainbeItS, such as .are lused for .heavy-duty. conveyors, belt :treads of tractors jand the like; to .provide improved means for i transmitting power fronr, a.' reciprocating. piston .1 utilizing both forward-and. return tstrokes. there- .offfordriving thebelt inithe same'direction. to provide improved meansfor reversing the.travel :ot the belt .as a wholepand to yprovide improved.v :means forkutilizing hydraulic power -fori the.; operation and control of such mechanism .as applied1 ftofa tractor.

These objects .are accomplished by .the illusvtrative: embodiments -off the invention shown .in

. thef accompanying drawings in which:

Figure l is. aside. elevation vpartly in sectionof a tractor tread member of the tracklaying belt :type equipped with operating rmechani'sm con- ;structed' according to-this invention.

Fig...2 isa horizontal; sectionwoi` the supporting l Fig. 5'showingz amodied form oftpawlsshfting emechanism.

Fg- 8 is a section of the same taken-.onthe-fline v8-810i Fig.":7. v

Fig. -9 iis.: asf' schematic zdia'gramillustrating the 1 arrangement :and operation Vof a hydraulicisystem forf supplying rpower to; and' fior P controlling the .beltedrving mechanism.

E Fig.; l0 is zacschematic sectional 1 detail fof da -forrrr offvalvex'suitableI for regulatingr Athefflow-`v of .'.-hy.dr.aulicVVA medium zto.- the.operatinglfmechanism -fofea tractor havirigia rpair of 1tractor`f-blts, such eas". the .ionef of Fig f located `Eat opposite f sides rof'fa lvehicle frame.

It is1we'llknown'thatfin tractors, having -belt Mtreads rsu'ch.: for zexampleiaslthe" tractors; ofsfmin- .zing :machinery for i which thefisubj ect-matter tof i the .adrawings fis particularly;I designed,'.'.the1ive f'hicle framefstru'ctureris nsuaillytcarried-rbywne l orzmorev pairs i oftractionizbeltsfzinathe form of Vencllessxchain ground-gripping structures .placed iside byfside.

Figures 1 to 6, inclusive, of the draWingsillus- :trate the structure.- and.operating-:mechanism of one,-of. such:y .beltscf andvFig. =9 shows the.' method of hydraulically. controlling a', Ypairof such.belts f 2 for ,simultaneous forward and reverse operation .-andfor operation` in respectively different.. directions and at different speeds relative to each other for` the purpose ofdriving and steering the tractor.

Each belt-carrying frame comprisesa-pairef plate-like frame members H rigidly'k connected .together .in parallel relation to eachv other and provided with suitable .tracks for lguiding .the links-of the .belt l2..between sprocket wheels.. I3 at the opposite ends of the frame. A ,horizontally disposed hydraulic cylinder I4 is .rigidly mounted in the frame and has a piston I5 Whose piston-rod i6 is pivotally connected at llitoaa rollers I I9 and mounted to'reciprocate-inrunf Yways formed by parallel tracks 2D, locatedparal- 4lel-vvithand midwaybetween the upper .andlower .horizontalruns ofthe traction belt.

' Thecross head lhas. a .pair .of .connection members inthe form of double-acting latch bars 2| mounted vto slide vertically vtherein.-.and-.bo`th v.endszof eachpf these members serve .asI paw-1s fshifstable to positions for Vcoacting .With-...the spindles 22 or other suitable shouldersr ofeither l the .upper or the lower run of the belt for driving .the belt infeithendirection of travel. .Thestruc- 'ture ofthe cross-.headL and its gpaWl-operating mechanism iszillustrated on a largerscale in Figs. .'4-and.5 where it will be seen that the latchl members 2| -are vertically slidable in "guideways formed in the .cross head I8. Each member 2 Lis yieldably :positioned for coaction Witheither run of the belt I2 by a pair of opposed helical springs 23./and 24 .seatedin Ygrooves 25 inthe opposed faces of the members- 2l. The springs 23`andv 24 bear in vopposed relation to each 4other. fbetvveen shoulders v26 on themernloer 2| andallug 21 .that is carried byvla4 rack bar 28. Theserack bars are mounted inways in theinteriorffof-fthe -cross head lesse; asto'fmeshand coact with-.na ypinion 29 whereby the rack bars are shiftedczin opposite directions soas -to carry their respective lpawls into position forcoacting with V:opposite 'runslvof ,the belt. The Ymembers 2l have, their lou-ter, ends beveled,;as shown ingFig. 5,:.so:.,that each of its pawls drives the chain when the piston moves in one directionxzand .yields I Lagainstrathe action of'- its springs to slippast..the -rodse22 v*when the .piston moves it in thereverseidrection. Thus as the'.pistonreciprocates one. memberrZl Willadrive one run of thebelt*duringpnexidirection of piston ,.movement and. the other member -2 l'fwillfdrive the; other runvof the belt Whencthe `piston moves in the reverse' direction.

fStop :pins .30 extend into: grooves` 3l fin .fthe ...latch members ,-1 2 l. andthe movements of i lsuch latch members under the actionof theirisprings ..23 and-24 are limited by shouldersatthe ends of Ye-Lgrooves ;3I. vThus the pin4 30 zandigroovefl crossheadll, which is carried by ball bearing determine the range of movement of the respective latch member 2I and the position of the lug 21 determines which run of the belt I2 will be engaged by the latch member. In the position shown in Fig. 5, the springs 23 will be under greater compression strain than the springs 24 when the latch members are in the position shown in Fig. 5, and will control the latching action of the pawls; The springs 24 will be likewise under greater compression strain when the position of the racks 2-3 as reversed by rotation of the pinion 29 and the pawls will then drive the chain in the reverse direction.

The pinion 29 is fast on a shaft 32 journaled in the cross head I8 and in a bracket 33 that extends outward therefrom through an opening 34 in the side frame II. The shaft 32 has a pinion 35 fast thereon which meshes with a rack 36 actuated by a wire 31 that runs through a flexible tube 31.I to a convenient position on the vehicle where it can be shifted manually, as for example, by le'ver 9I.I or 9I.2.

The sprocket I3 which carries the traction chain beit I2 at the end of the frame that is at the right in Figs. 1 and 2 and at the left in Fig. 3, is journaled in a cross head 38 that is slidably mounted in guide ways 39 for taking up the slack in the traction belt I2 and this cross head 38 is shifted longitudinally of the frame by a connecting rod 48 driven by the piston 4I of a cylinder 42.

In Fig. 2, the cylinders I4 and 42 are shown partly in section and partly in plan; whereas in Fig. 1, the side plate frames I I are partly broken away to show these cylinders and their connections with their cross heads in elevation. The

cylinder I4 is provided with ports 43 and 44 at its opposite ends for the admission and escape of hydraulic fluid for driving its piston I in opposite directions and the cylinder 42 has ports 45 and 46 for the flow of fluid to and from the chambers at the ends of the piston 4 I. The piping which connects these ports for hydraulic operation of the pistons is not shown in Figs. 1, 2 and 3 but is indicated diagrammatically in Fig. 9.

In Figs. 2 and 3, the valve which controls the reverse movements of the chain-driving piston I5 is indicated at 41 and has a spool 48 which is rotated in its casing to control its ports in wellknown ways.

Rotation of the spool 48 in one direction is controlled by a dog 48 coacting with an arm 58 on the spool 48 and reverse rotation of the spool 48 is controlled by a dog 5I that coacts with the arm 52'on the spool 48. The dogs 49 and 5I are adjustably mounted on a rod 53 that is aflixed to an arm 54 on the bracket 33 which reciprocates `with the cross head I8. The rod 53 is slidably mounted in a stationary bracket 55.

In the modified form shown in Figs. 7 and 8, the driving of the chain belt I2 is accomplished by a single pawl 56 that is shiftable in the cross head 51 so as to engage the spindles 22 of the upper run of the belt, as illustrated in Fig. '1, and to clear those of the lower run of the belt, or to be shifted downwardly to engage the spindles 22 of the lower run of the belt and clear those of the upper run. In this case, the body portion of the cross head 51 is in the form of a hydraulic cylinder 58 and the pawl 56 is in the form of piston rods extending through opposite heads of the cylinder 58 and having a central piston portion 59 that is shiftable by hydraulic pressure at opposite sides thereof.

The cylinder 58 is accordingly provided with ports 60 and 6I controlled by a valve, such as the valve 41, through the movements of the cross head so as to shift the pawl 56 from one belt run to the other at the opposite ends of the travel of the cross head 51 under the power furnished by the hydraulic cylinder I4.

When the invention is applied to operation of the traction belts of a crawler tractor, there are usually two units placed side by side and rigidly connected together by a suitable frame struc-- ture, not shown in the drawings.

An illustrative schematic diagram of hydraulic mechanism for the operation and control of a tractor unit, comprising a pair of such tractor belts, is shown in Fig. 9 of the drawings. In this drawing, the parts of the separate belt systems are designated by the same reference numerals as the corresponding parts shown in the other views of the drawings but are distinguished by characters with decimal suffixes .I and .2 respectively. The piping as shown comprises main supply lines for the traction cylinders I4.I and I4.2, a pilot line for controlling the larger valves of the power line to these cylinders, and a third line to the take-up cylinders.

In Fig. 9 the reservoir for the hydraulic uid supply is designated by the numeral 62. The uid is drawn from the reservoir 62 by a pump 63 and delivered through pipe 64 to branch pipes 65.I and 65.2 to the belt driving cylinders I4.I and I4.2 respectively. Fluid escaping from the cylinders is conducted by pipes 66.I and 66.2 from which it flows through return pipe 61 back to the reservoir 62.

The pilot valve 41.I controls the cylinder I4.I in cooperation with a four-way power line control valve 68.I for reversing the movement of the piston I5.I by alternately reversing the connection between the ports 43.I and 44.I of the cylinder 4I.I with the pressure line 65.I and the return line 66.I.

Similarly, valve 41.2 and valve 68.2 control the supply and discharge of operating fluid to the cylinder I4.2 through power pipe 65.2 and return pipe 66.2. The connections to the ports 44.I and 44.2 are made direct with the pipes 65.I and 65.2 respectively and the corresponding ports of valves 68.I and 68.2 are closed by plugs 88.3. This arrangement compensates for the fact that the piston rod occupies part of the cylinder area on one side of the piston and assures that equal total pressures drive the piston in both directions of its movement.

A manually controlled throttle valve 69 controls the amount of power uid passing from the supply pipe 64 to the pipes 65.I and 62.2 and thus controls the speed of travel of the belts I2.

The pipes 65.I and 65.2 are also controlled differentially by a manually controlled valve 10 for steering purposes. A suitable structure for the steering valve 10 is shown schematically in Fig. 10. In the form shown, the power line 64 communicates with a central chamber 1I in the valve casing and the pipes 65.I and 65.2 connect with chambers 12 and 13 respectively. The flow from the chamber 1I to the chambers 12 and 13 is controlled by a plunger-like spool 14 which slides through a bore 15 extending through the end walls of the valve and the partition walls which separate the chambers 1I, 12 and 13. The spool has a contracted neck 16 in-ts mid-portion with tapered portions 11 and 18 at opposite ends of the neck 16.

These tapered portions 11 and 18 are spaced so that when the spool 14 is in the middle position in which it is shown, equal quantities of liquid will pass 'from the pipe 64 to the pipes 65.! and 65.2. When the spool lis shifted toward the iglt of Fig. 10; the flow of liquid to the pipe 65.! will be` gradually reduced and finally cut ol entirely. When the spool is shifted toward the left of Fig. 10, the iiow of uid from pipe 65 to pipe 65.2 will be correspondingly cut off and reduced. Thus by shifting the spool, the relative speeds of travel of the two traction belts can be controlled by manipulating the valve 10.

A by-pass connection '!9 between the pipes 64 and 8l controlled by a check valve 89 permits the pump 63 to be operated at a speed somewhat in excess of the demands of the system.

Hydraulic pressure for automatic operation of the valves 68.! and 88.2 is provided through supply lines 8!.! and 8!.2 connected to the pipe 64 and return lines 82.! and 82.2 connected to the return pipe 61.

A four-way valve `83.1 controls the connection between the pipes 8!.! and 82.! with alternative extension lines 84.! and B5.!, which lines are reversed in their relation to the extension lines 88.! and 87.! through the shifting of the spool of the four-way valve 4H.

The pipes 86.! and 87.! are each connected to jack means 88.! for operating the spool of the four-way valve 88.!. The valve 83.! is controlled manually through the shifting of its spool 89.! by a cam 99.! controlled by a hand lever 9!.!. The cam 99.! has angularly spaced high points 92.! corresponding to the limiting positions of the lever 9L! and a low point 93.! midway between the high points 92.! as indicated by the arrow 94.!.

Levers 9L! and 9!.'2 are the same levers, hereinbefore referred to, that operate the control wires 3'! in the form shown in Figs. 1 to 5 inclusive or the control valves (not shown) that operate the piston 59 in the form shown inl Figs. 7 and 8. The limiting positions of said levers indicated by arrows 94.! and 94.2 correspond respectively to reverse directions of travel of the traction belts at opposite sides of the vehicle body. The function of the valves 83.! and 83.2 and cams 90.! and 98.2 is to reverse or modify temporarily the pressures on the motor pistons !5.! and !5.2 to reduce the frictional resistance on pawls 2! or 58 and permit them to shift easily for reversing the travel of the traction belts when levers 9!.! and 9!.2 are shifted from one limit of their throw to the other.

The control mechanism shown at the right side s of Fig. 9 is identical with that shown Vat the left side and herebefore-described and is identied by corresponding numerical .characters distinguished vby the decimal suix .2.

The belt tensioning cylinders 42.! and 42.2 are connected to the pipe 64 by feed pipe 85 through branch lines 95.! and 95.2, with a by-pass line 98 connecting the pipe 95 to the return flow pipe 61. This by-pass line is controlled by a bleeder valve 9'! whereby the pressure on the pistons of the cylinders 42.! and 42.2 may be regulated. The :air chamber 98 allows for some resilience in the take-up elect of the cylinders 42.! and 42.2.

Although some of the structure shown has been specically described, it will be understood that numerous details of the structure shown may Vbe altered or omitted without departing from the vspirit of the invention as defined by the following runs Amoving in opposite directions, .ross'head mihtd t reciprocate lon-V iidinally between said runs, `and latchmeans .carried by .said crosshead and operativeto drivingly ngag''onerunlof said'belt when the crosshead-moves in one direc-- tionand to drivingfly-engage Athe other run of f'said belt when said crosshead lmoves inthe `opposite direction, said vlatch means comprising 4a driving element finovable on said fcros'shead -from -a lposi* tion Vfordriving'on'e of said belt runs in one direction yto raposition Vfor driving the other belt run inthe same direction, and a second driving .element movable on said crosshead between posi'- tions -for driving said belt runs in theopposite directions, said 4eler'nents'being of ratchet'pawl formation adapted to drive the respective belt runs 'in one -direction of travel and to withdraw inthe yother direction of travel.

2. A chain belt drive, comprising an endless chain belt arranged to provide 4Va pair of parallel runsmoving in opposite directions, a Icross'h'e'ad mounted to reciprocate longitudinally between said runs, motor means operative to reciprocate saidecross'head, latch means carried'by Said crosshea'd and operative to drivingly engage one '-run of said belt when the crosshead moves in "one direction and to drivingly engage the 'other run of said `belt when said crosshead moves in the opposite direction, said latch means comprising a pair of Vconnected ratchet pawls shiftable Aonsaid crosshead transversely to the belt 'runs for `alter-- natively 'driving them in the direction of travel of the crosshead, a vsecond pair of connected ratchet pawls shiftable on said cros'shead trans`- versely to the belt runs for alternatively driving them inthe opposite direction of travel A'of the crosshead.

3. A 'device of the class described, comprising a chain belt 'having yparallel runs traveling in relatively `opposite directions, a `driving member mounted to travel forward and back longitudinally of said belt runs, a pair of pawls carried by said driving `'member and interconnected for alternatively driving 4one or the other of said belt runs 'during the travel of said driving member 'in one direction. a second pair of pawls carried "by said driving member and vinterconnected for al'- ternatively driving 'one or the other -of said belt runs during the travel of said driving member in the opposite direction, and reversible holding means for positioning said pairs of interconnected pawls with one pawl of one pair in drive ing relation to one run of 'the belt while one Apawl of the other pair is Ain driving relation to the other run of the belt and vice versa.

4. A device of the lclass described, comprising a chain belt having parallel runs traveling in relativelypopposite directions, a driving member chain `'beltarranged to provide a pair of parallel mounted to travel forward and back longitudinally of said belt runs., a pair of pawls carried by said udriving member and interconnected for alternatively driving one or the other of said belt runs during the travel of said driving member in one direction, a second pair of pawls carried by said driving member and interconnected for alternatively driving one or the other of said belt runs during the travel of said driving member in the opposite direction, and reversible holdf ing means for positioning said pairs of .interconnected pawls with one pawl of one Apair in driving relation to one run of the belt while one pawl of the other pair is in driving relation tothe other run of the belt and vice versa, said holding means comprising shiftable abutment means and individual springs interposed between each said pawl and said abutment means for yieldingly holding the pawls in their respective belt-driving positions, each said pawl being shaped to cam itself out of driving relation with the belt when the driving member reverses its direction of travel from the respective driving direction for which such pawl is held.

5. A device of the class described, comprising a chain belt having parallel runs traveling in relatively opposite directions, a driving member mounted to travel forward and back longitudinally of said belt runs, a pair of latch bars carried by Said driving member and each disposed transversely to the direction of travel thereof and slidable lengthwise from a position of driving relation to one run of said belt to a position of driving relation to the other run, reversible holding means to position said latch bars for simultaneous driving relation to respectively diierent runs of said belt, one of said latch'bars having its opposite ends both formed to serve as paWls to have driving relation to respective belt runs during one direction of travel o said driving member and to be cammed out of such driving relation during the other direction of travel of said driving member, the other latch bar having its ends both formed to serve as pawls for driving relation to their respective belt runs only during said other direction of travel of said driving member and to be cammed out of such relation during said one direction of travel, and reversible holding means for causing one of said latch bars to coact with one of said belt runs and the other said latch bars to coact with the other said belt run, and vice versa.

6. A device of the class described, comprising a chain belt having parallel runs traveling in relatively opposite directions, a driving member mounted to travel forward and back longitudinally of said belt runs, a pair of pawls carried by said driving member and interconnected for alternatively driving one or the other of said belt runs during the travel of said driving member in one direction, a second pair of pawls carried by said driving member and interconnected for alternativelyr driving one or the other of said belt runs during the travel of said driving member in the opposite direction, and reversible holding means for positioning said pairs of interconnected pawls with one pawl of one pair in driving relation to one run of the belt while one pawl of the other pair is in driving relation to the other run of the belt and vice versa, said holding means comprising a pinion journaled on said driving member between said belt runs, 4a pair of racks respectively meshing with opposite sides of said pinion for movement in opposite directions to each other toward and away from each of said belt runs, and springs between said pawls and said racks for yieldingly urging the respective said pawls toward their belt-driving positions.

'7. A device of the class described, comprising a chain belt having parallel runs traveling inA relatively opposite directions, a driving member mounted to travel forward and back longitudinally of said belt runs, a pair of latch bais carried by said driving member and each disposed transversely to the direction of travel thereof and slidable lengthwise from a position of driving relation to one run of said belt to a position of driving relation to the other run, one of said latch bars having its opposite ends both formed to serve as parvis to have driving relation to the respective belt runs during one direction of travel of said driving member and to be cammed out of such driving relation during the other direction of travel of said driving member, the other latch bar having its ends both formed to serve as pawls for driving relation to their respective belt runs only7 during said other direction of travel of said driving member and to be cammed out of such relation during said one direction of travel, and reversible holding means for causing one of said latch bars to coact with one of said belt runs and the other said latch bar to coact with the other said belt run, and vice versa, said holding means comprising a pinion journaled on said driving member between said belt runs, a pair of racks respectively meshing with opposite sides of said pinion for movement in opposite directions to each other toward and away from each of said belt runs, and springs between said latch bars and said racks for yieldingly urging said pawls toward their belt driving positions.

8, A chain belt drive, comprising an endless chain belt arranged to provide a pair of parallel runs moving in opposite directions, a crosshead mounted to reciprocate longitudinally between said runs, latch means carried by said crosshead and operative to drivingly engage one run of said belt when the crosshead moves in one direction and to drivingly engage the other run of said belt when said crosshead moves in the opposite direction, said latch means comprising a driving element shiftable from one run of the belt to the other run for alternatively driving such runs in one direction, and a second driving element shiftable from one run to the other for alternatively driving such runs in the opposite direction, means for reversibly shifting said driving elements to reverse the travel of the belt runs.

9. A chain belt drive, comprising an endless chain belt arranged to provide a pair of parallel runs moving in opposite directions, a crosshead mounted to reciprocate longitudinally between said runs, latch means carried by said crosshead and operative to drivingly engage one run of said belt when the crosshead moves in one direction and to drivingly engage the other run of said belt when said crosshead moves in the opposite direction, said latch means comprising a driving element movable on said crosshead from a position for driving one of said belt runs in one direction to a position for driving the other belt run in the same direction, and a second driving element movable on said crosshead between positions for driving said belt runs in the opposite directions, said elements being of ratchet pawl formation adapted to drive the respective belt runs in one direction of travel and to withdraw in the other direction of travel, and control means interposed between said driving elements adapted to engage them with respectively opposite runs of said belt for one direction of belt travel and to reverse their relation to the belt runs for the reverse direction of belt travel.

10. A chain belt drive according to claim '7, in which the springs are arranged in pairs bearing between abutments on respective racks and the opposite end portions of the respective latch bars so that the shifting of the racks positions the pawls for yielding relation to either belt run.

ll. A chain belt drive, comprising an endless chain belt arranged to provide a pair of parallel runs moving in opposite directions, a crosshead mounted to reciprocate longitudinally between said runs, a double acting hydraulic motor piston connected to said crosshead for reciprocating the crosshead, latch means carried by said crosshead and operative to drivingly engage one of said belt runs when the crosshead moves in one direction and to drivingly engage the other said belt run when said crosshead moves in the opposite direction, said latch means being movable on said crosshead from a position for driving said belt in one direction of travel to a position for driving said belt in the reverse direction of travel through the reciprocating movement of said crosshead, means controlling said latch means to reverse the direction of travel of the belt as a whole, manually operative means for actuating said latch control means, valve means controlling the pressures on opposite sides of said motor piston, and means actuated by said man- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 479,297 McCarthy July 19, 1892 653,726 Yarnell July 17, 1900 

